Also, because DSR exist, so you can still avail of a lot of the 1440p goodies (textures etc) in games if you have the FPS to spare if you decide to use 1080p instead.
1080p also have another advantage is that your lowest 'playable resolution' (IE, the resolution where there wouldn't be any blur) is lower, so if you decided that a game is too demanding at 1440p, you can drop to 1080p and still have relatively sharp images. Going the other way round induces unfixable blur.
There is also blurring if you DSR from 1080p to 1440p, but that can be largely fixed with a little DSR smoothing, but there is no known solution to the blur caused by going from 1440p to 1080p.
144hz with G-Sync or FreeSync is, IMHO, one of the very spoiling purchases, as now I may not be able to tolerate anything without them lol.